Why does my iphone 4 freeze on the sleep mode screen?

[iMore Question]

Twice my iphone 4 has frozen in the sleep mode with a black screen. I know the phone is working in the background but I cannot activate it by pressing the menu button on the bottom.

I even have trouble hard rebooting as both buttons don't seem to work. After many attempts, it finally allows me to reboot the phone but not without a lot of frustration.

Why is my phone doing this? Is it about to crash?

 

[kch50428]

...as both buttons don't seem to work...

may be a hardware issue...

 

[legalservices15]

Thanks for the info.

What can I do to fix it?

 

[kch50428]

Refer to qualified service personel... An Apple Genius Bar... Authorized Service Center... or other cellular repair provider.

 

[legalservices15]

Thanks for your time and suggestion.

I will do as recommended.